Image converter tube



July 19, 1960 J. BRUHIN IMAGE CONVERTER TUBE Filed April 28, 1958 INVENTOR JOSEPH BRUHIN ORNEY United States Patent-Ofiice 2,945,975 Patented. July 19, .1960

HVLA'GE CONVERTER TUBE Joseph Bruhin, Zurich, Switzerland, assignor to Albiswerk Zurich, A.G., Zurich, Switzerland, a corporation of Switzerland Filed Apr. 28, 1958, Ser. No. 731,434

7 Claims. (Cl. 313-94) The present invention relates to image converter tubes. More particularly, the present invention relates to an improved image converter tube arrangement wherein the accelerating electrode thereof can be protected during fabrication.

Various types of image converter tubes are conventionally used today. For example, some image converter tubes include a-photowathode surface which is responsive to infrared rays. Any infrared rays which impinge on the photocathode surface are converted into electrons. These electrons are accelerated by one or more accelerating electrodes so as to impinge upon a fluorescent screen arranged at the other end of tube. The electrons impinge on the fluorescent screen thereby providing a visible image of the infrared rays which had impinged upon the photo-cathode surface.

The photo-cathode surfaces are made up of different materials such as cesium and/orsilver deposited on the inner surface of the photo-cathode screen. This deposition usually takes place within the hermetically sealed envelope of the image converter tube so that the process may be carried out in a vacuum. I

During the deposition process, it is essential that none of the deposited material be permitted to reach those surfaces of the accelerating electrodes which are subjected to an intense accelerating field. Otherwise, during operation of the image converter tube, the deposited material would emit electrons and distort the image to be reproduced.

Conventional image converter tubes have been constructed wherein attempts were made to overcome this problem. These usually required the insertion of some form of shield between the photo-cathode'surfaces and the accelerating electrode from a position outside of the tube envelope. This required additional entry portions in the form of tubes to be provided in the tube envelope. After the deposition process has been carried out, these tubes are sealed off. The difliculties with such arrangements are that the forming of the additional glass tubes in the glass envelope weakens the tube structure and causes an extremely high reject failure for the image converter tubes.

Inaccordance with the present invention, these disadvantages are overcome by providing shielded means within the tube envelope, without requiring additional entry means into the tube proper.

It is accordingly an object of the present invention to provide a new and improved image converter tube.

A second object of the present invention is to provide a new and improved image converter tube having one or more accelerating electrodes which are formed without attendant impurities.

Another object of the present invention is to provide a new and improved image converter tube having at least one accelerating electrode wherein blocking means are provided for protecting the accelerating electrode during deposition of material. on the photo-cathode surface.

Still another object of the. present invention is to provide a new and improved shielded device for image con verter tube accelerating electrons.

primarily consists of an image converter tube arranged Within a hermetically sealed envelope and adapted to have electrons flowing therein along a preselected path. 'At least one accelerating electrode is provided and is formed with an opening along the preselected path so that the electrons may pass therethrough. Blocking means are provided which may be moved between a blocking position wherein electrons are prevented from passing through the opening of the accelerating electrode and an open position whereinthe electrons are able to pass through such opening. Finally, supporting and locking means are provided for supporting the blocking means in its blocked position and for locking the blocking means in its open position whenever the same is moved into the open position thereof.

In a preferred embodiment of the present invention, locking means includes a pivotally mounted shielded member which may be pivoted between its blocked and open position. The supporting and locking means may include a pin member which is normally urged towards the shielding member by means of resilient urging means.

In another preferred embodiment of the present invention, the shielded member is provided with a passage therethrough that communicates with the resiliently urged pin member so as to cooperate with the same and lock the shielded member in its open position thereof.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method'of operation, together with additional objects, and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing which is a perspective view, partially in section of a portion of an image converter tube incorporating the principles of the present invention.

Referring to the drawing, it can be seen that theimage converter tube elements are mounted within aglass enve lopetube which is preferably hermetically sealed. The entire envelope and remaining portions of the image converter tube are not shown in order to avoid unnecessarily complicating the drawing.

Furthermore, these elements are constructed in a wholly conventional manner. The electrode system 1 includes a first accelerating electrode 4 and a second. accelerating electrode 5. The accelerating electrode 4 is formed with two adjacent cylindrical portions 21 and 22, cylindrical member 22 having a smaller diameter than cylindrical member 21. The electrode 4 has a disk shaped central portion 23. which substantially closes the mating portions of the cylinders 21 and 22 except for the opening 8 formed in the portion 23.

Adjacent the cylindrical portion 22 of the anode 4 is the second accelerating anode 5 which is formed with a second opening 24. It can be seen that openings8 and 24 are arranged to be coaxial with respect to the envelope 2. This permits electrons formed at the photo-cathode of the tube to proceed along a preselected axial path to the fluorescent screen. In the arrangements shown, the photo-cathode would be to the right of the illustrated portion of the image converter tube and the fluorescent screen would be to the left.

The intense accelerating electric field for accelerating the electrons towards the fluorescent screen is formed between the accelerating electrodes. 4 and 5. This field is formed between the adjacent portions of these electrodes.

before hermetically sealing the same and which may also be used for inserting the cesium and/ or silver material to be deposited upon the photo-cathode surface in the direction shown by the arrow 26. It is therefore essential to protect the above-listed portions of the accelerating electrodes 4 and 5 from being contaminated by the undesired cesium and/or silver deposits. For this purpose, an annular flange member 6 is provided which is connected along its outer circumferential edge to the inner surface of the envelope 2. In addition, the annular member 6 is connected along its inner annular surface to the outside surface of the electrode 4. This prevents any of the material being deposited from entering that portion of the tube between the electrodes 4 and 5 through that annular volume provided between the electrode 4 and the tube envelope.

In accordance with the present invention, a blocking member 7 is provided to protect the opening 8 in the disk portion 23 of the accelerating electrode 4. This blocking member 7 is shown in blocked position wherein the opening 8 of the electrode 4 is blocked so that the passage of electrons therethrough would be blocked. The blocking member 7 is pivotally mounted on the disk portion 23 of the electrode 4 by means of the threaded mounting member 9. It can be seen that the blocking member 7 is formed with a passage 12 therethrough, having a purpose which will be described hereinbelow.

The blocking member 7 is retained in the illustrated blocking position by supporting and locking means including a slideable pin member 11 which is normally urged against the blocking member 7 by means of the spring 10. It can be seen that the pin 11 is slideably mounted in tab portions 14-, 14 formed from the accelerating electrode 4. A cross member 27 is provided to stop the forward movement of the pin 11 after a preselected amount.

In operation, the electrode assembly is formed from the various elements illustrated in the drawing and positioned as shown in this drawing. The blocking member 7 is manually moved so that the opening path is completely covered and the spring 10 is arranged to resiliently urge the pin 11 against the blocking member 7 with suificient force to maintain the blocked member 7 in the illustrated blocking position. The deposition of the cesium and/or silver or the like elements can then be carried out in the conventional manner by means of the entry in tube 3. Once this deposition has been completed the tube 3 may be sealed off so as to result in a hermetically sealed envelope. After there is no longer any danger of the undesirable material contaminating the sensitive portions of the electrodes 4 and 5, the envelope 2 of the tube may be gently tapped or shaken with suflicient force to overcome the restraining force of the spring 10 so as to pivot the blocking member 7 in the direction of the arrow 28. After the blocking member 7 has pivoted a suiiicient amount, the free end portion of the pin 11 will communicate with the passage 12 through the blocked member 7 so as to cooperate therewith and prevent further motion of the blocking member 7. No matter how much the envelope is now shaken, it is no longer possible for the blocking member to be moved back into the blocking position once it has been moved to the open position illustrated in the dotted lines in the drawing.

It should be apparent that since the blocking member 7 is in block position, the sensitive areas of the accelerating electrodes are completely protected from undesired contamination. The blocking member 7 completely protects the opening 8 of the accelerating electrode 4 while the annular flange member 6 protects the remaining entry portion f r. the ontaminating mat ial.-

It is therefore seen that the above described arrange ment provides a new and improved image converter tube wherein it is unnecessary to weaken and strain the tube envelope in order to provide proper shielding means for the sensitive portions of the accelerating electrodes.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of hermetically sealed tubes differing from the types described above.

While the invention has been illustrated and described as embodied in an image converter tube, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an image converter tube wherein electrons are adapted to flow along a preselected path, in combination, an hermetically scalable envelope; at least one accelerating electrode arranged in said envelope and being formed with an opening in the preselected path of the electrons so that the electrons may pass therethrough; blocking means mounted within said envelope and adapted to be moved between a blocking position wherein said opening of said accelerating electrode is closed and an open position wherein the electrons may pass through said opening; and a passage passing through the blocking means, a slideable element locking means movably mounted within said envelope in contact with peripheral portions of said blocking means for releasably supporting said blocking means in the blocking position, and for allowing movement of the blocking means toward the open position by an impact upon the envelope insufficient to cause rupture of the tube; biasing means for moving said slideable element locking means within said envelope, said movement of the biasing means being in response to movement of said blocking means to the open position, said biasing means moving said slideable locking means to a position positively engaging said passage of said blocking means for locking said blocking means in the open position.

2. In an image converter tube wherein electrons are adapted to flow along a preselected path, in combination, an hermetically scalable envelope; a pair of spaced accelerating electrodes arranged in said envelope, each of said electrodes being formed with an opening in the preselected path of the electrons so that the electrons may pass therethrough; blocking means arranged in said euvelope and having a movable member mounted on one of said electrodes near its opening and adapted to be moved between a blocking position wherein said opening of each of said accelerating electrodes is closed and an open position wherein the electrons may pass through said opening; a passage passing through said movable member, and a slideable locking means mounted within said envelope positioned for frictionally engaging peripheral portions of said member and temporarily restraining movement thereof in its blocking position and for allowing movement of said movable member to its open position when an impact is applied to the envelope; spring biasing means for moving said slideable locking means, in response to movement of said movable member to its open position, to a position positively engaging said passage of said movable member and locking said movable member in the open position.

3. In an image converter tube wherein electrons are adapted to flow along a preselected path, in combination,

an hermetically sealable envelope; at least one accelerating electrode arranged in said envelope and being formed with an opening in the preselected path of the electrons so that the electrons may pass therethrough; pivotal blocking means having a member mounted on said electrode for pivoting along the face of said electrode between a blocking position wherein said opening of said accelerating electrode is closed and an open position wherein the electrons may pass through said opening; a passage passing through said member, and a slideable pin locking means mounted within said envelope positioned for frictionally engaging peripheral portions of said member and temporarily restraining movement thereof in its blocking position and for allowing movement of said member to its open position when an impact is applied to the envelope; spring biasing means for moving said locking means, in response to movement of said member to its open position, to a position positively engaging said passage of said member and locking said member in the open position.

4. In an image converter tube wherein electrons are adapted to flow along a preselected path, in combination, an hermetically sealable envelope; at least one accelerating electrode arranged in said envelope and being formed with an opening in the preselected path of the electrons so that the electrons may pass therethrough; blocking means in said envelope having a member mounted on said electrode for movement between a blocking position wherein said opening of said accelerating electrode is closed and an open position wherein the electrons may pass through said opening; a slideable pin moveably mounted on said electrode for frictional engagement with peripheral portions of said member when said member is in the blocking position, resilient biasing means urging said pin into frictional engagement with said member with a force suflicient to allow movement of said member toward the open position when the envelope is subjected to an impact insufiicient to rupture parts of the tube, a recess in said member positioned in the path in which said pin is urged when said member is in the open position and adapted to receive said pin for locking said member in said open position, whereby the tube may be activated when the opening is blocked and the opening may be permanently unblocked by shock of said impact after the tube is sealed.

5. In an image converter tube wherein electrons are adapted to flow along a preselected path, in combination, an hermetically sealable envelope; at least one accelerating electrode arranged in said envelope and being formed with an opening in the preselected path of the electrons so that the electrons may pass therethrough; blocking means including a flat member pivotally mounted on said electrode for movement along a face thereof between a blocking position wherein said opening of said accelerating electrode is closed and an open position wherein the electrons may pass through said opening; a pin movably mounted on said electrode for frictional engagement with peripheral portions of said member when said member is in the blocking position, resilient spring means urging said pin into frictional engagement with said member with a force sufiicient to allow movement of said member toward the open position when the envelope is subjected to an impact insufiicient to rupture parts of the tube, a recess in said member positioned in the path in which said pin is urged when said member is in the open position and adapted to receive said pin so as to lock said member in said open position; whereby the tube may be activated when the opening is blocked and the opening may be permanently unblocked by shock of said impact after the tube is sealed.

6. An image converter as set forth in claim 5 wherein said recess in said member is a hole passing through the flat surface of the member.

7. An image converter as set forth in claim 5 wherein said resilient means includes a compression spring spiralled around said pin.

References Cited in the file of this patent UNITED STATES PATENTS 2, 149, 849

OTHER REFERENCES V Lubszynski Mar. 7, 1939 

